[1] US Air Force, Med Grp 78, Aerosp Med 78, Occupat Med Serv, New York, NY 10037 USA
[2] Natl Inst Occupat Safety & Hlth, Ctr Dis Control & Prevent, Div Surveillance Hazard Evaluat & Field Studie, Cincinnati, OH USA
[3] Natl Inst Occupat Safety & Hlth, Ctr Dis Control & Prevent, Div Appl Res & Technol, Cincinnati, OH USA